This application is the national phase under 35U.S.C. xc2xa7371 of PCT International Application No. PCT/KR00/00133 which has an International filing date of Feb. 19, 2000, which designated the United States of America and was published in English.
The present invention relates to an apparatus for preventing vacuum compression of a scroll compressor, and in particular, to an apparatus for preventing vacuum compression of a scroll compressor by which even if a compressor is continuously operated in a state that coolant does not flow into an inlet of a suction tube as the suction tube is clogged the coolant is partially leaked to a low pressure chamber, so that the inside of the compressor is not reduced to an ultra-vacuum state.
Generally, compressors in use for air conditions or refrigeratorsserve to convert mechanical energy to compression energy of a compressible fluid. Compressors mainly include a reciprocating type compressor, a scroll type compressor, a centrifugal type compressor (normally called a turbo type compressor), and a vane type compressor (normally called rotary type compressor).
Among them, the scroll compressor sucks and compresses gas by using a rotor to discharge it, which is like the centrifugal compressor or the vane compressor. In contrast, the reciprocating compressor uses a linear movement of a piston for the same purpose.
The scroll compressor includes a low pressure scroll compressor or a high pressure scroll compressor depending on whether a suction gas is filled inside a closed container or a discharge gas is filled therein.
FIG. 1 shows a general low pressure scroll compressor in use for the air conditioners or the refrigerators.
As shown in the drawing, the upper and the lower frames 4 and 4xe2x80x2 are fixedly installed at the upper and lower portion of the inside a closed container 3. A suction tube 1 for sucking a coolant gas and a discharge tube 2 for discharging the high pressure coolant gas are respectively installed at one side of the closed container 3.
A drive motor 17 consisting of a stator 20 and a rotor 18 is fixedly installed between the upper frame 4 and the lower frame 4xe2x80x2.
A fixing (fixed) scroll 5 is combined by a bolt 5xe2x80x2 at the upper side of the upper frame 4, and an orbiting scroll 7 is rotatably combined with the fixing scroll 5 at the lower side thereof, having a plurality of compressive chambers for compressing a coolant sucked from the suction tube 1.
A wrap W1 is formed in an involute shape at the inner surface of the fixing scroll 5, and an inlet 5a is formed at the outermost side of the wrap W1, communicating with the suction tube 1. An output 5b is formed at the upper side of the central portion of the closed container, communicating with the discharge tube 2.
A wrap W2 is engaged to be revolved on the inner surface of the orbiting scroll 6 in the fixing scroll 5.
At the lower side of the orbiting scroll 6, a drive shaft 13 is combined at the central portion of the rotor 18, penetrating the upper frame 4. The drive shaft 13 is provided with an oil passage 13a formed to penetrate the central portion in the length direction and an eccentric portion 3b formed at the upper portion thereof.
An oil feeder 16 is installed at the lower portion of the drive shaft 13 to pump oil 15 filled at the lower portion of inside the closed container 3.
A slide bush 19 is insertedly formed at the eccentric portion 13b of the drive shaft 13, which is varied in the radial direction and receives a rotational force of the drive shaft 13 in the tangential direction. An Oldham""s ring 21 a rotation-preventing unit, is combined at the lower portion of the orbiting scroll 6 to prevent the orbiting scroll 6 from rotating.
A high pressure and low pressure separating plate 8 is fixedly installed at the upper side of the fixing scroll 5 by a plurality of bolts 22. A gas discharge hole 8a is formed at the central portion of the upper side of the fixing scroll 5. The inside of the closed container 3 is divided into a high pressure chamber 10 and a low pressure chamber 14 by the high and low pressure separating plate 8. At one side of the high and low pressure separating plate 8, a back pressure valve 12 is combined to partially discharge the gas of the high pressure chamber 10.
A discharge chamber 23 is formed at the upper portion of the high and low pressure separating plate 8, communicating with the gas discharge hole 8a and the discharge tube 2. At the side of the discharge hole 5b, a bypass hole 25 is formed to be connected with an intermediate pressure 24 formed between the fixing scroll 5 and the orbiting scroll 6. A bypass valve 26 is installed at the upper side of an inlet of the upper portion of the bypass hole
The operation of the scroll compressor of the background art constructed as described above will now be explained.
When the rotor 18 is rotated by an applied current, the drive shaft 13 is rotated as being eccentric as long as the eccentric distance of the eccentric portion 13b according to the rotation of the rotor 18, so that the orbiting scroll 6 is circularly moved.
Prevented from rotating by the Oldham""s ring 21, that is, the rotating-prevention unit, the orbiting scroll 6 makes turning movement centering around the drive shaft 13, drawing a turning circle at a distance apart as long as the turning radius. At this time, as the orbiting scroll 6 makes turning movement at the distance apart as long as the turning radius, a plurality of compressive chambers 7 are formed between the fixing scroll 5 and the two wraps W1 and W2.
Accordingly, a coolant gas filled in the compressive chambers 7 by being sucked through the inlet 5a placed at one side of the fixing scroll 5 is moved toward the center of the scrolls 5 and 6 by the continuous turning movement of the scrolls 5 and 6. While being moved, its volume is reduced to be compressed, discharged through the outlet 5b of the fixing scroll 5 and passed through the high and low pressure separating plate 8 to flow into the high pressure chamber 10. And this coolant gas flown into the high pressure chamber 14 is introduced to a condenser (not shown) through the discharge tube 2.
At this time in case that the pressure of the coolant being discharged to the high pressure chamber 10 is too high, the back pressure valve 12 is forced to open so as to discharge a portion of the coolant to the low pressure chamber 14, so that an abnormal over-compression can be prevented from occurring.
In addition, when the drive shaft 13 is rotated, the oil 15 is pumped by the oil feeder installed at the lower end portion of the drive shaft 13 and supplied upwardly through the oil passage 13a, so that a friction resistance of a thrust face 4a of the upper frame 4 that contacts the orbiting scroll 6 is reduced.
However, the scroll compressor of the background art has the following problem. That is, in the abnormal pressure condition due to the over-compression, the gas can be moved by the back pressure valve. But, in case that a pipe line through which the coolant is circulated is partially clogged and thus the coolant is prevented from sucking to the sucking tube, though the compression is continuously made in the compressive chamber, the pressure of the high pressure chamber does not go beyond a pre-set pressure at which the back pressure valve is operated. Consequently, the inside of the compressor becomes a vacuum state, and if this vacuum state is maintained for a certain time, the inside of the compressor becomes ultra-vacuum state, causing a short in a charging portion of the drive motor due to degradation of electric insulation, resulting in a high possibility that the drive motor is damaged and an electric shock occurs due to a leakage current.
In addition, since oil is not sufficiently supplied to the thrust face of the upper frame contacting the orbiting scroll at the initial state of driving the compressor, the contacting portion is easily abraded.
FIG. 2 shows another example of a scroll compressor in accordance with the background art.
In describing the scroll compressor, the same reference numerals are given for the same elements as in FIG. 1, for which descriptions are omitted.
As shown in the drawing, a valve stopper 3a is combined at the central portion of the upper surface of the fixing scroll 5, communicating with an outlet 5b of the fixing scroll 5. A check valve 30 is installed inside the valve stopper 3a to control flowing of the coolant gas of high temperature and high pressure as compressed in the compressive chamber 7, for which the check valve 30 is moved upwardly and downwardly along a guide face xe2x80x98Gxe2x80x99 of the inner side of the valve stopper 3a to open and close the outlet 5b of the fixing scroll 1a. 
A discharge hole 3axe2x80x2 is formed at the upper surface of the valve stopper 3a. 
The operation of another example of the scroll compressor of the background art constructed as described above will now be explained.
According to the scroll compressor of the another example, in case that the scroll compressor stops operating for a short time and starts 3 r operating, the check valve 30 serves in a manner that the gas of the high pressure chamber 10 flows back to be introduced into the compressive chamber 7 formed by the wraps W1 and W2 of the fixing scroll 5 and the orbiting scroll 6 through the outlet 5b of the fixing scroll 5, to thereby reversely rotate the orbiting scroll 6, so that the wraps W1 and W2 can be prevented from damaging and a noise does not occur. Besides, in order to prevent a degradation of the compression efficiency, the check valve 30 clogs the outlet 5b to thereby prevent the orbiting scroll 6 from reversely rotating against reverse discharging.
Meanwhile, the coolant gas compressed in the compressive chamber 7 pushes up the check valve 30 placed at the front end through the outlet 5b of the fixing scroll 5, so as to be discharged. At this time, the check valve is moved along the inner wall of the valve stopper 3a to start a stroke, and as the compressor is continuously being operated, the check valve is placed in a raised position, maintaining contacting the face of the upper end portion of the valve stopper 3a. 
Since the check valve 30 is placed in the raised position while the compressor is operated, the compressed coolant gas is discharged through the discharge hole 3axe2x80x2 of the valve stopper 3a. When the compressor stops operating, the discharge gas filled in the upper portion of the closed container 3 applies a force to the upper surface of the check valve 30 through the discharge hole 3axe2x80x2 of the valve stopper 3a, then, the check valve 30 rapidly closes the discharge hole 5b of the fixing scroll 5, thereby preventing the discharge gas from flowing back.
However, disadvantageously, the scroll compressor according to the second background art has a structure that in case that the compressor keeps operating in a state that the coolant does not flow into the inlet, the high-pressure discharge gas won""t be bypassed toward the low pressure side, for which there is no device or structure provided in preparation for occurrence of vacuum at the suction side possibly caused when a cooling cycle is interrupted.
Accordingly, for the products adopting the scroll compressor, a service valve (not shown) is installed to connect an indoor device and an outdoor device. In this respect, if the scroll compressor is started in a state that the service valve is locked up, the coolant gas being introduced to the low pressure side gradually dies away, pushing into a high vacuum state, resulting in that a drive motor is exposed in the high vacuum, so as to be damaged due to the vacuum discharge, the temperature of the discharge gas goes up due to the high compression ratio, and the compressive unit is abraded due to shortage in supply of oil.
In addition, if such abnormal operation of the compressor is continued for a long time, vacuum of the low pressure chamber and the compressive chamber, that is, the suction pressure region, is accelerated, resulting in that a hermetic terminal (not shown) is damaged due to the vacuum compression or tip-sealing is degraded due to the re-compression by the compressive unit to be broken down. Thus, a reliability of the compressor is inevitably degraded.
Thus, in order to overcome the above problem, an object of the present invention is to provide an apparatus for preventing vacuum compression of a scroll compressor which is capable of preventing the inside of a compressor from being an ultra vacuum state when a pipe line is clogged. so that its drive motor can be prevented from breaking down, the temperature of a discharge gas due to a high compression ratio can be prevented from increasing, and a compressive unit can be protected by being successively supplied with oil.
Another object of the present invention is to provide an apparatus for preventing vacuum compression of a scroll compressor which is capable of preventing a vacuum compression of a compressor by using an intermediate pressure.
Still another object of the present invention is to provide an apparatus for preventing vacuum generation of a scroll compressor which is capable of preventing the inside of the compressor from becoming a vacuum state as well as preventing a thrust face from abrading.
In order to achieve the above objects, there is provided an apparatus for preventing vacuum compression of a scroll compressor including: a suction tube and a discharge tube each combined to one side of a closed container filled with oil to an adequate height; a fixing scroll having a wrap and a coolant inlet and an outlet; a high and low pressure separating plate installed at the upper side of the fixing scroll, dividing the inside of the closed container into a high pressure chamber and a low pressure chamber, the high and low pressure separating plate having a gas discharge hole at its central portion; an orbiting scroll having a plurality of compressive chambers for compressing a sucked coolant by;,being rotatably engaged with the wrap of the fixing scroll at the lower side of the fixing scroll, and having a wrap for rendering each compressive chamber to have different pressure to be successively moved as being turned; and a high vacuum preventing unit installed at the inner side of the body of the fixing scroll.
In order to achieve the above objects, there is also provided an apparatus for preventing vacuum compression of a scroll compressor in which the fixing scroll and the orbiting scroll are rotated in the compressive chamber to compress a coolant and oil supplied through an oil passage is supplied to a thrust face of an upper frame of the scroll compressor as a drive shaft is being rotated, including a back pressure line formed at the orbiting scroll so that a compressive chamber can communicate with the thrust face to discharge a portion of the coolant gas compressed in the compressive chamber of the scroll compressor to the low pressure chamber.
In order to achieve the above objects, there is also provided an apparatus for preventing vacuum generation of a scroll compressor in which a valve stopper is combined to the upper portion of a discharge hole formed at the fixing scroll, a check valve is installed in the scroll compressor to be moved upwardly and downwardly along a guide face of the inside of the valve stopper to control flowing of the coolant gas of high pressure and high temperature compressed in the compressive chamber, to open and close the discharge hole of the fixing scroll, including: a mutually communicating by-pass hole for by-passing a high pressured coolant gas to a low pressure side at the time when the check valve closes the discharge hole of the fixing scroll.